C语言switch分支内if语句计算税款无输出问题求助

核心错误点 #

• switch分支顺序错误：default分支写在了case 1前面，输入1时会优先匹配default分支直接退出，永远不会执行case 1的逻辑，这是无输出的核心原因
• scanf读取收入的语法错误：一是格式符不能用%.2lf，scanf不支持精度限制，应改为%lf；二是缺少取地址符&，应该传入&income而非income；三是格式串末尾多余的\n会要求用户多输入一次换行才会结束读取
• 范围判断逻辑错误：C语言不支持0 < income <= 24000这类连续比较写法，实际执行时会先判断0 < income得到布尔值0或1，再判断这个值是否<=24000，导致判断永远为真，必须拆分为income > 0 && income <= 24000的逻辑与写法
• 分支覆盖不全：缺少收入超过58000的处理逻辑，也未实现报税身份2、3、4的计算逻辑
• 错误判断逻辑冗余：case 6~9的分支可以省略，default已经可以覆盖所有非1-5的输入场景

修复后完整代码 #

#include<stdio.h>

int main()
{
    // 声明：status=报税身份，income=收入，taxOwed=应缴税款
    int status;
    double income, taxOwed;

    // 打印菜单
    printf("************Menu****************\n");
    printf("1) Single\n");
    printf("2) Married Filing Jointly\n");
    printf("3) Married Filing Separately\n");
    printf("4) Head of Household\n");
    printf("5) Exit\n");
    printf("\n");
    printf("********************************\n");
    printf("\n");
    printf("Enter status : ");
    scanf("%d", &status);

    // 业务逻辑处理
    switch(status)
    {
        case 5:
            printf("\n");
            printf("Exit Program...\n");
            break;
        case 1:
            printf("Enter your taxable TI: $");
            scanf("%lf", &income);
            if (income > 0 && income <= 24000)
            {
                taxOwed = income * 0.15;
                printf("\nThe taxes owed are: $%.2lf", taxOwed);
            }
            else if (income > 24000 && income <= 58000)
            {
                taxOwed = 3600 + 0.28 * (income - 24000);
                printf("\nThe taxes owed are: $%.2lf", taxOwed);
            }
            else
            {
                printf("\nIncome out of current calculation range.");
            }
            break;
        case 2:
        case 3:
        case 4:
            printf("This filing status is not implemented yet.");
            break;
        default:
            printf("You entered a wrong status. Program Exit . . .");
            break;
    }

    return 0;
}

内容的提问来源于stack exchange，提问作者NewB123